Components on machines such as aircraft have a fatigue life that depends on factors including number of hours used and severity of use. A particular component may be used on one aircraft and later installed on another, making tracking these parameters a challenge. The present application provides several ways to accomplish this tracking.
Severity of use may be determined by measuring strain. One way to provide a low power strain measurement for fatigue life calculation was to turn power off, avoiding exciting strain sensors and supporting electronics except when sampling, as described in the '777 application. But the ability to reduce power was limited by the substantial amount of current drawn by the strain sensors and amplifiers during sampling. Especially in situations where the measurement required frequent sampling or turning on power rapidly to take a measurement, high power was needed. Not only did high bandwidth amplifiers that turn on quickly use more power they also introduced additional noise. And the power used by the system increased with the rate at which data was sampled. The high power consumption and high cost associated with providing sufficient power restricted the use of such systems. Thus, a better system for monitoring strain for fatigue life calculation is needed, and this system is provided by the present patent application.